It's super frequently recommended as a starting point for learners because it's high level enough to get something on the screen in ten lines of code but low level enough to teach you the fundamentals of how the rendering pipeline works (even though GL's abstraction is rather anachronistic and differs from how modern GPUs actually work). Vulkan (requiring literally a thousand LoC worth of initialization to render a single triangle) is emphatically not any sort of replacement for that use case (and honestly not for 95% of hobbyist/indie use cases either unless you use a high-level abstraction on top of it).

The worst thing about OpenGL is probably the hilariously non-typesafe C API.